Conventionally, as the wire material for coil such as motors and the like, the round wire, in which an insulating coating is provided on the core wire (copper wire) having a cross-sectional shape in a round shape, is used. However, there is a problem that: voids are formed between adjacent round wires; and the void ratio becomes high, when the round wire is wound in multi layers. Because of this, for example, the insulated electric wire having a hexagonal cross section is known as described in Japanese Unexamined Patent Application, First Publication No. 2003-317547 (Patent Literature 1 (PTL 1)). When the cross section of the insulated electric wire is hexagonal, wires can be aligned for each side to be contacted. Thus, there is an advantage of reducing the voids in the wounded state. In addition, the insulated electric wires having the hexagonal cross section are described in Japanese Unexamined Patent Application, First Publication No. 2008-147062 (Patent Literature 2 (PTL 2)) and Japanese Unexamined Patent Application, First Publication No. 2009-134891 (Patent Literature 3 (PTL 3))
As a method for forming the insulating coating of the insulated electric wire, the immersing method, the application method, and the electrical deposition method are known. The immersing method and the application method are the methods, in which the conductive wire material (copper wire) to be the core material of the insulated electric wire is immersed in the coating material; or the coating material is applied on the surface of the wire material. Then, the coating material is dried, and then, baked to form the insulating coating on the surface of the wire material.
The electrodeposition method is a method in which the insulating coating is formed by electrodepositing a coating component on the surface of copper wire: by passing the copper wire to be the core material of the insulated electric wire through the electrodeposition solution including a coating component; and by applying electrical current on the copper wire. The electrodeposited coating component is subjected to a backing treatment to form the insulating coating. The insulated electric wires described in PTLs 1 and 2 are examples in which the insulating coating is formed by the application method. The insulated electric wire described in PTL 3 is an example in which the insulating coating is formed by the immersing method.